The disclosure of Japanese Patent Application No. HEI 10-235807 filed on Aug. 21, 1998, including the specification, drawings and abstract, is incorporated herein by reference in its entirety.
1. Field of the Invention
The present invention relates to a fuel tank for storing fuel and a vehicle equipped with the fuel tank.
2. Description of the Related Art
Japanese Patent Application Laid-open No. HEI 8-170568 discloses a fuel tank that is designed to reduce the capacity of an upper space defined above the surface of liquid fuel in the fuel tank in order to reduce fuel vapor that occurs in the upper space in the fuel tank.
This fuel tank has a fuel storing chamber that is defined by an expandable surrounding bag made of a film, and a housing to which the surrounding film bag is mounted. The surrounding film bag is made up of an upper wall, a lower wall, and bellows-like side walls connecting the upper and lower walls. The lower wall of the surrounding film bag is fixed to a flat bottom wall of the housing.
When fuel is supplied into or discharged from the fuel storing chamber via a fuel passage connected to the fuel storing chamber, the upper wall of the surrounding film bag moves up or down following changes in the amount of fuel present in the fuel storing chamber. Corresponding to the movement of the upper wall, the side walls expand or contract. In this manner, the space defined above the surface of liquid fuel in the fuel storing chamber is controlled or reduced in size.
However, although the bellows side walls of the surrounding film bag of the fuel tank contract in accordance with a decrease in the amount of fuel in the fuel tank, the contraction of the side walls is limited. Therefore, when the amount of fuel in the fuel tank decreases to or below a predetermined level, a substantial upper space capable of holding fuel vapor is created above the surface of liquid fuel. As the amount of fuel further decreases, the upper space increases in size, thereby impeding minimization of fuel vaporization.
Accordingly, it is an object of the present invention to provide a fuel tank having a fuel storing chamber that changes in capacity in accordance with the amount of fuel stored therein, wherein fuel vaporization can be considerably reduced and a predetermined effective fuel-storing capacity of the fuel storing chamber can be secured. It is another object of the invention to provide a vehicle equipped with such a fuel tank.
In accordance with one aspect of the invention, a fuel tank includes a partition deformable in accordance with an amount of fuel stored in a fuel storing chamber defined by the partition, a fuel passage connected to the fuel storing chamber for supplying fuel to or discharging fuel from the fuel storing chamber, and a residual fuel discharging passage capable of discharging a remaining amount of fuel without being discharged via the fuel passage due to a curvature of a lower wall of the fuel storing chamber occurring when the lower wall curves upwards in accordance with a decrease in the amount of fuel stored in the fuel storing chamber.
In this fuel tank, the lower wall partially defining the fuel storing chamber curves upwards in accordance with a decrease in the amount of fuel stored in the fuel storing chamber. Therefore, the volume of gaseous space in the fuel storing chamber is reduced by an amount corresponding to the reduction in the capacity of the fuel storing chamber caused by the curvature of the lower wall, in comparison with a conventional fuel tank in which a lower wall does not deform. Although the upward curvature of the lower wall may cause an amount of fuel may to remain near a peripheral end portion of the lower wall without being discharged via the fuel passage, this remaining fuel is discharged via the residual fuel discharging passage, thereby minimizing the amount of residual fuel in the fuel storing chamber.
In the fuel tank of the invention, the residual fuel discharging passage may be connected to the fuel storing chamber in such a manner that, when the lower wall is curved, a lower side edge portion of an opening of the residual fuel discharging passage to the fuel storing chamber is lower than an opening of the fuel passage to the fuel storing chamber.
Therefore, a remaining amount of fuel that is not discharged from the fuel storing chamber via the fuel passage remains near a peripheral end portion of the lower wall of the fuel storing chamber due to the upward curvature of the lower wall. This remaining amount of fuel is discharged from the fuel storing chamber via the residual fuel discharging passage connected to the fuel storing chamber, since at the time of the curvature of the lower wall, the lower side edge portion of the opening of the residual fuel discharging passage to the fuel storing chamber is lower than the opening of the fuel passage to the fuel storing chamber.
In the fuel tank of the invention, the fuel storing chamber may be defined by an upper wall having a polygonal shape, a lower wall having a polygonal shape and facing the upper wall, and a peripheral wall extending between the upper wall and the lower wall.
The fuel tank of the invention may further have a construction wherein the fuel passage is connected to the lower wall and the residual fuel discharging passage is connected to the peripheral wall in such a manner that a lower side edge portion of an opening of the residual fuel discharging passage in the peripheral wall is lower than an opening of the fuel passage formed in the lower wall at least when the lower wall is curved to a maximum extent.
Therefore, a remaining amount of fuel not discharged from the fuel storing chamber via the fuel passage is retained near a peripheral end portion of the lower wall of the fuel storing chamber due to the upward curvature of the lower wall. This remaining amount of fuel is discharged from the fuel storing chamber via the residual fuel discharging passage connected to the peripheral wall since at the time of the maximum upward curvature of the lower wall, the lower side edge portion of the opening of the residual fuel discharging passage in the peripheral wall is lower than the opening of the fuel passage in the lower wall.
The fuel tank may also have a construction wherein the fuel passage is connected to the lower wall and wherein the residual fuel discharging passage is connected to the lower wall in such a manner that at least when the lower wall is curved to a maximum extent, a lower side edge portion of an opening of the residual fuel discharging passage in the lower wall is lower than an opening of the fuel passage formed in the lower wall.
Therefore, an amount of fuel that is not discharged from the fuel storing chamber via the fuel passage connected to the lower wall but remaining near a peripheral end portion of the lower wall of the fuel storing chamber due to the upward curvature of the lower wall is discharged from the fuel storing chamber via the residual fuel discharging passage connected to the lower wall, since at the time of the maximum upward curvature of the lower wall, the lower side edge portion of the opening of the residual fuel discharging passage in the lower wall is lower than the opening of the fuel passage in the lower wall.
The fuel passage may be connected to a substantially central portion of the lower wall, and the residual fuel discharging passage may be connected to a portion of the lower wall that is near a corner portion of the lower wall.
The fuel tank may also have a construction wherein the fuel passage is connected to the peripheral wall and wherein the residual fuel discharging passage is connected to the peripheral wall in such a manner that at least when the lower wall is curved to a maximum extent, a lower side edge portion of an opening of the residual fuel discharging passage in the peripheral wall is lower than an uppermost portion of the lower wall and than a lower side edge portion of an opening of the fuel passage in the peripheral wall.
Therefore, an amount of fuel that is not discharged from the fuel storing chamber via the fuel passage connected to the peripheral wall but remains near a peripheral end portion of the lower wall of the fuel storing chamber due to the upward curvature of the lower wall is discharged from the fuel storing chamber via the residual fuel discharging passage connected to the peripheral wall, since at the time of the maximum upward curvature of the lower wall, the lower side edge portion of the opening of the residual fuel discharging passage in the peripheral wall is lower than the uppermost portion of the lower wall and than the lower side edge portion of the opening of the fuel passage in the peripheral wall.
In the fuel tank constructed as described above, the lower wall partially defining the fuel storing chamber curves upwards in accordance with decreases in the amount of fuel stored in the fuel storing chamber. Therefore, the volume of gaseous space in the fuel storing chamber is reduced by an amount corresponding to the reduction in the capacity of the fuel storing chamber achieved by the curvature of the lower wall, in comparison with a conventional fuel tank in which a lower wall does not deform. Hence, fuel vaporization can be considerably reduced. Furthermore, an amount of fuel that is not discharged from the fuel storing chamber via the fuel passage but remains near a peripheral end portion of the lower wall due to the curvature of the lower wall is discharged via the residual fuel discharging passage, so that the residual fuel amount of the fuel storing chamber is minimized. Hence, a predetermined effective fuel-storing capacity of the fuel storing chamber can be secured.
The fuel tank of the invention may further include an auxiliary fuel tank that temporarily stores the fuel. In this case, the residual fuel discharging passage discharges into the auxiliary fuel tank the amount of the fuel that remains without being discharged via the fuel passage.
In accordance with another aspect of the invention, a fuel tank includes a partition deformable in accordance with an amount of a fuel stored in a fuel storing chamber defined by the partition, and a fuel passage connected to the fuel storing chamber for supplying the fuel into the fuel storing chamber or discharging the fuel from the fuel storing chamber. The fuel storing chamber is defined by an upper wall having a polygonal shape, a lower wall having a polygonal shape and facing the upper wall, and a peripheral wall extending between the upper wall and the lower wall. The lower wall curves upwards in accordance with a decrease in the amount of the fuel. The fuel passage is connected to the peripheral wall in such a manner that when the lower wall is curved, a lower side edge portion of an opening of the fuel passage in the peripheral wall is lower than an uppermost portion of the lower wall.
In this fuel tank, the lower wall partially defining the fuel storing chamber curves upwards in accordance with decreases in the amount of fuel stored in the fuel storing chamber. Therefore, the volume of gaseous space in the fuel storing chamber is reduced by an amount corresponding to the reduction in the capacity of the fuel storing chamber achieved by the curvature of the lower wall, in comparison with a conventional fuel tank in which a lower wall does not deform. Furthermore, an amount of fuel that remains near a peripheral end portion of the lower wall of the fuel storing chamber due to the upward curvature of the lower wall is discharged from the fuel storing chamber via the residual fuel discharging passage connected to the peripheral wall, since at the time of the curvature of the lower wall, the lower side edge portion of the opening of the residual fuel discharging passage in the peripheral wall is lower than the uppermost portion of the lower wall. Therefore, this fuel tank can minimize the residual fuel amount of the fuel storing chamber while requiring a simpler construction than the above-described fuel tank according to the first aspect. Hence, it becomes possible to secure a predetermined effective fuel-storing capacity of the fuel storing chamber at low costs.
In accordance with still another aspect of the invention, fuel tank-equipped vehicle includes a fuel tank as in the first aspect, wherein the fuel storing chamber is tilted relative to a horizontal direction, and the residual fuel discharging passage is connected to a substantially lowermost portion of the fuel storing chamber.
In this vehicle, since the fuel storing chamber is tilted relative to a horizontal direction, an amount of fuel remaining in the fuel storing chamber at the time of an upward curvature of the lower wall resides at and near the lowest point in the fuel storing chamber, and therefore can be efficiently discharged via the residual fuel discharging passage. Hence, a predetermined effective fuel-storing capacity of the fuel storing chamber can be secured.